1. Field of the Invention
The present invention relates to an electronic component which is durable against stress.
2. Description of the Related Art
In general, as shown in FIG. 9, an electronic component 100 is in many cases used in a structure in which an electronic element 10 is mounted on a thermal diffusion plate 14 with an insulating board 12 therebetween. When such a mounting structure is employed, a crack or the like may be formed in the insulating board 12 due to thermal stress or residual stress when the electric component is subjected to a thermal cycle, ultimately resulting in an adverse effect on the characteristics of the electronic element 10.
In consideration of this, there is known a structure in which a stress-alleviating member 16 made of aluminum and having a plurality of through holes formed therein is provided between the insulating board 12 and the thermal diffusion plate 14. It is said that, with this structure, superior thermal conduction can be achieved between the insulating board 12 and the thermal diffusion plate 14, improvement is realized in a heat dissipation performance from the electronic element 10, and the influence by the stress can be reduced due to a function of a stress-absorbing space including the through holes.
In addition, there is known a technique in which, in a ceramic circuit board having a ceramic board and a metal plate which is directly joined on a surface of the ceramic board and which primarily comprises aluminum, a thinned thickness section, having a thickness of ⅙ to ⅚ that of the portion of the metal plate on which the metal plate is mounted, is provided inside of the outer periphery portion of the metal plate, to reduce the influence of the stress.
Moreover, there is known a technique in which, when a steel plate which serves as a base member and a silicon chip which is an electronic component are joined with solder therebetween, a cut-out section is formed over the entire outer periphery of the joining surface of the silicon chip and the steel plate and the silicon chip are joined, so that the stress is spread out and alleviated.
As described, in an electronic component of a layered structure, there must be employed a structure in which the influence of stress with respect to the thermal cycle or the like is reduced.
However, in the electronic components of the related art, when a crack is formed in a part of the layered structure, the crack may extend to the joining interface and may reach a portion directly below the electronic element, possibly resulting in an increase in the thermal resistance from the electronic element to the thermal diffusion member or an increase in insulation deficiency, and, consequently, prevention of an improvement in the reliability or an increase in the lifetime of the electronic component.
In addition, a special member such as the stress-alleviating member must be provided in order to suppress the extension of the crack, possibly resulting in a secondary problem such as an increase in the manufacturing cost of the electronic component.